not a native letter in Old English; in Anglo-French words it represents the "ts" sound (as in Anglo-French fiz, from Latin filius, modern Fitz); from late 13c. it began to be used for the voiced "s" sound and had fully taken that role by 1400. For letter name, see zed.

Thou whoreson Zed, thou vnnecessary Letter. ["King Lear," II.ii.69]

Series of zs to represent a buzzing sound first attested 1852; zees "spell of sleep, a nap" is slang first recorded 1963, American English student slang.

comic performer, 1580s, from French zani, from Italian zani, zanni "a zany, clown," originally Zanni, Venetian dialect variant of Gianni, pet form of Giovanni "John;" thus equivalent to English Jack. A stock character in old comedies, he aped the principal actors.

"passionate ardor in pursuit of an objective or course of action," late 14c., from Old French zel (Modern French zèle) and directly from Late Latin zelus "zeal, emulation" (source also of Italian zelo, Spanish celo), a Church word, from Greek zelos "ardor, eager rivalry, emulation," "a noble passion" [Liddell & Scott], but also "jealousy;" prom PIE *ya- "to seek, request, desire." From mid-15c. as "devotion."

early 14c., "member of a militant 1st century Jewish sect which fiercely resisted the Romans in Palestine," from Late Latin zelotes, from Greek zelotes "one who is a zealous follower," from zeloun "to be zealous," from zelos "zeal" (see zeal). Extended sense of "a fanatical enthusiast" first recorded 1630s (earlier in this sense was zelator, mid-15c.).

"full of zeal" (in the service of a person or cause), 1520s, from Medieval Latin zelosus "full of zeal" (source of Italian zeloso, Spanish celoso), from zelus (see zeal). The sense "fervent, inspired" was earlier in English in jealous (late 14c.), which is the same word but come up through French. Related: Zealously, zealousness.

c. 1400, from Middle French zede, from Late Latin zeta, from Greek zeta, from Hebrew zayin, letter name, literally "weapon;" so called in reference to the shape of this letter in ancient Hebrew. U.S. pronunciation zee is first attested 1670s. Other dialectal names for the letter are izzard, ezod, uzzard, and zod.

1848, from German Zeitgeist (Herder, 1769), "spirit of the age," literally "time-spirit," from Zeit "time" (from Proto-Germanic *tidiz "division of time," from PIE root *da- "to divide") + Geist "spirit" (see ghost (n.)). Carlyle has it as a German word in "Sartor Resartus" (1840) and translates it as "Time-Spirit."

"point of the heavens directly overhead at any place," late 14c., from Old French cenith (Modern French zénith), from Medieval Latin cenit, senit, bungled scribal transliterations of Arabic samt "road, path," abbreviation of samt ar-ras, literally "the way over the head." Letter -m- misread as -ni-.

The Medieval Latin word could as well be influenced by the rough agreement of the Arabic term with classical Latin semita "sidetrack, side path" (notion of "thing going off to the side"), from se- "apart" + *mi-ta-, a suffixed form of PIE root *mei- (1) "to change, go, move." Figurative sense of "highest point or state" is from c. 1600.

mid-14c., from Old English Zefferus, from Latin Zephyrus (source also of French zéphire, Spanish zefiro, Italian zeffiro), from Greek Zephyros "the west wind" (sometimes personified as a god), probably related to zophos "the west, the dark region, darkness, gloom." Extended sense of "mild breeze" is c. 1600. Related: Zephyrean.

"figure which stands for naught in the Arabic notation," also "the absence of all quantity considered as quantity," c. 1600, from French zéro or directly from Italian zero, from Medieval Latin zephirum, from Arabic sifr "cipher," translation of Sanskrit sunya-m "empty place, desert, naught" (see cipher (n.)).

A brief history of the invention of "zero" can be found here. Meaning "worthless person" is recorded from 1813. As an adjective from 1810. Zero tolerance first recorded 1972, originally U.S. political language. Zero-sum in game theory is from 1944 (von Neumann), indicating that if one player wins X amount the other or others must lose X amount.

1580s, "a single word (usually a verb or adjective) made to refer to two or more nouns in a sentence" (but properly applying to only one of them), from Greek zeugma, "a zeugma; that which is used for joining; boat bridge," literally "a yoking," from zeugnynai "to yoke" (from PIE root *yeug- "to join").

supreme god of the ancient Greeks and master of the others, 1706, from Greek, from PIE *dewos- "god" (source also of Latin deus "god," Old Persian daiva- "demon, evil god," Old Church Slavonic deivai, Sanskrit deva-), from root *dyeu- "to shine," in derivatives "sky, heaven, god." The god-sense is originally "shining," but "whether as originally sun-god or as lightener" is not now clear.